Field of the Invention
The invention relates in general to a frequency deinterleaving and time deinterleaving circuit, a method thereof and a receiving circuit of a digital television, and more particularly to a frequency deinterleaving and time deinterleaving circuit, a method thereof and a receiving circuit that can be configured to support multiple digital video standards.
Description of the Related Art
There have been numerous digital television standards, including Digital Video Broadcasting-Terrestrial (DVB-T), Digital Video Broadcasting-Cable2 (DVB-C2), Digital Video Broadcasting-Terrestrial 2 (DVB-T2), Digital Terrestrial Multimedia Broadcast (DTMB), and Integrated Services Digital Broadcasting-Terrestrial (ISDB-T). These different standards are broadcasted and promoted respectively in different regions. Among these standards, DVB-C2, DVB-T2, DTMB and ISDB-T adopt interleaving-deinterleaving schemes in frequency and time domains to minimize various interferences and/or noises have on transmission data during signal transmission. FIG. 1 shows a function block diagram of a conventional receiver of a digital television. The receiver 100 of a digital television mainly includes a front-end circuit 110, a frequency deinterleaving circuit 120, a time deinterleaving circuit 130, a demapping circuit 140, and a decoding circuit 150. An input signal is usually a modulated signal, e.g., a quadrature amplitude modulation (QAM) signal based on orthogonal frequency division multiplexing (OFDM). The front-end circuit 110 performs operations including but not limiting to fast Fourier transform (FFT), channel estimation, equalization and signal-to-noise (SNR) estimation on the input signal, and outputs an interleaved signal that carries including but not limiting to information such as two quadrature components (I and Q), an SNR, or channel state information (CSI). The information is rearranged in a correct sequence after the frequency deinterleaving circuit 120 and the time deinterleaving circuit 130 perform deinterleaving operations, and is restored to bit information after an operation performed by the demapping circuit 140. Next, the transmission data is obtained after an operation (e.g., low-density parity check (LDPC) or Viterbi decoding operation) performed by the decoding circuit 150. It should be noted that, the above DVB-T2 standard further includes a cell interleaving and deinterleaving operation. Therefore, a cell deinterleaving circuit is further included in a DTB-T2-compatible receiver.
The time interleaving and deinterleaving operations mainly involve two operation concepts—convolution and row-column operations. The ISDB-T standard and the DTMB standard adopt the convolution operation, and the DVB-T2 standard and the DVB-C2 standard adopt the row-column operation. Further, the frequency interleaving and deinterleaving operations also involve two main operation concepts—look-up table (LUT) and permutation operations. The ISDB-T standard adopts the look-up table operation, and the DTMB, DVB-T2 and DVB-C2 standards adopt the permutation operation. For both frequency deinterleaving and time deinterleaving, a memory (e.g., a static random access memory (SRAM) or a first-in-first-out (FIFO) memory) is provided for temporary data storage. By writing the information into and reading the information from the memory, the sequence of the information is restored. However, implementation details may slightly vary although the same operation concept is adopted. For example, the DVB-T2 standard and the DVB-C2 standard both adopt the row-column operation concept for time interleaving and deinterleaving, the DVB-C2 standard adopts specifically a twisted row-column operation concept. In conclusion, the receiver 100 of different standards requires a memory to implement frequency and time deinterleaving operations for one of different standards. For a receiver 100 compatible to multiple standards, memory devices may be configured inefficiently if each of these standards utilizes an separate circuit for frequency deinterleaving and time deinterleaving.